In recent years, along with increasing speed of a wireless communication system, a MIMO (Multiple Input Multiple Output) technique of transmitting data from a plurality of antennas and receiving data by a plurality of antennas has been employed to many wireless standards of wireless LAN, mobile communication, and others, from a viewpoint of improving a frequency utilization efficiency.
In one-to-one wireless communication (Point to Point) between one transmitting station and one receiving station, an eigenmode propagation method which is disclosed in Non-Patent Document 4 is known as a method of maximally bringing out a communication capacity provided by a wireless propagation path. In this eigenmode propagation method, the capacity provided by the propagation path is maximally brought out by carrying out the eigendecomposition (Singular Value Decomposition) to a channel matrix H as a property of the wireless propagation path between the transmitting/receiving antennas and carrying out the weighted calculation to a matrix obtained by the eigendecomposition with a transmitting vector signal and a receiving vector signal. In a system that quasi-static environment is assumed such that a user does not move so much as a wireless LAN, variation of the wireless propagation path is small, and therefore, this method is suitable.
From a viewpoint of information theories, many studies have been made for a communication capacity of one-to-N wireless communication (BC: Broadcast Channel) having “N” receiving stations for one transmitting station and a communication capacity of M-to-one wireless communication (MAC: Multiple Access Channel) having one receiving station for “M” transmitting stations. Regarding the communication capacity of the Broadcast Channel, “Dirty Paper Coding” has been introduced as a method of providing an upper limit of a system capacity in Non-Patent Document 1, and Non-Patent Document 2 has proven that a method of maximally bringing out the capacity exists.
And, Non-Patent Document 3 discloses an idea of a method of improving the throughput of the entire system by the coordinated cooperation of a plurality of transmitting stations to apparently increase the total number of antennas on the transmitting-station side and carrying out the above-described Dirty Paper Coding.
In a conventional wireless communication system, methods in simultaneous transmission from a base station to a terminal are known, a method of dividing frequencies among adjacent base stations (FDMA: Frequency Division Multiple Access) and reusing the frequencies at distant locations by designing a cell structure, and a method of CDMA (Code Division Multiple Access) in which, even when a plurality of base stations carry out the transmission at the same frequency, the transmission is multiplexed by a code, and a signal is extracted by the same code on the receiving side. Also, a method of time-dividing a plurality of base stations (TDMA: Time Division Multiple Access) is known. Further, in recent years, as disclosed in the above-described documents, an idea of a method of carrying out the communication with a plurality of terminals by spatial division (SDMA: Space Division Multiple Access) by the cooperation of the plurality of base stations has been also disclosed. These multiple access techniques are determined and operated based on a standard of a system.
In a next-generation standard of cellular communication, as disclosed in Non-Patent Document 5, an idea of coordinated communication between a plurality of base stations, which carries out the transmission by the cooperation of the plurality of base stations, has been disclosed.